Not Applicable
Not Applicable
Air springs have many applications within vehicle suspension systems and are often referred to as struts, or suspension members utilizing pressurized air or gas as a compressible elastic medium between a structurally spaced load and support, which also may utilize oil as a dampening medium. By this definition the present invention is herein referred to as a gas strut. Gas struts are commonly used in off-road applications as either complimentary support mounted in addition to other vehicle supports, such as coil, leaf or torsion springs, or as the sole means of vehicle support.
The application of using a gas strut as the sole means of vehicle support is problematic in that air and gas provide very low spring rates from full strut extension throughout much of the first portion of the strut""s compression stroke, causing the vehicle to lean significantly when driven on the side of a hill, and also during hard turns. Vehicle roll-overs are possible in these conditions when in the extreme. One of the more popular embodiments of an off-road gas strut is the long-travel gas strut. Unfortunately, the longer the travel, or stroke, the more pronounced the aforementioned problem becomes. Some off-road enthusiasts and off-road racers have resolved this problem by either installing additional struts, or springs, or by increasing the gas pressure within the strut. These solutions, however, result in a harsh and unpleasant ride as added springs or strut gas pressures may exceed the ideal spring pressure to vehicle weight ratio, and excessively high strut gas pressures can cause the strut piston to effectively hydraulic lock prior to achieving a complete compression stroke. Thus, a dual mode spring rate which can automatically change with respect to driving conditions would be an ideal improvement.
The following are references to prior art suspension systems that should provide a basis for general comparison to the present invention. Other patent references are listed for review in the references cited section but not explained herein.
Pat. Appl. No. 706798 is a velocity sensitive dual rate shock strut using fluid as a damping medium and gas trapped in a primary chamber above the fluid as a spring is modified by adding a secondary chamber with an orificed inlet to the primary chamber above the normal fluid level. On extreme deflections, the fluid level within the strut reaches the orifice which severely restricts flow therethrough to cause a second greatly increased spring rate for the gaseous spring which also is velocity sensitive.
Pat. Appl. No. 166416 is an adjustable rate air spring having a flexible membrane with a spring rate adjustable by adding or removing fluid or air through an external connection.
Pat. Appl. No. 696475 is a dual volume air spring for suspensions in which a post like closer closes a communication port between primary and secondary chambers when the primary chamber air bag is sufficiently compressed.
Pat. Appl. No. 407319 is an automatic suspension leveling system employing automatic gas levelers at each wheel, a reservoir, electrically operated valves, electric height position sensors and a compressor.
Pat. Appl. No. 216644 is a self-pumping hydropneumatic shock strut which levels the vehicle via a pumping action which activates oil transfer from a low pressure area to a high pressure area thus reducing the effective compressible area of the spring, or high pressure area. Said invention is therefore similar in function to other inventions which automatically alter spring rate by changing fluid volume within the strut.
These and other prior art suspension systems either (1) operate in a soft spring rate for the initial strut deflection distance and then provide either a second, harder spring rate or more restrictive dampening only after a lengthy compression or deflection, and/or (2) the spring rate is adjustable by adding or removing gas or fluid. In some prior art suspension systems this addition or removal of gas or fluid is accomplished automatically by load leveling sensors which actuate remote pumps in communication with gas reservoirs to vary pressures to the struts with the higher loads, or to the struts detected to require additional support to level the vehicle.
These devices, however, do not respond quickly enough to be as beneficial in high speed off-road sport or racing applications as is the present invention. To minimize the effect of vehicle roll a quick strut response to vehicle inclination and centrifugal force is crucial. Struts which require extreme suspension deflection before providing a multiplied spring rate inherently allow excessive vehicle sag, or roll, before compensation begins to take effect, and increased dampening by itself will not help to support the load side of the vehicle, but only delay vehicle leaning effect.
One object of the present invention is to improve on prior art suspension systems with an integral twin gas chamber shock strut, independent of external power sources and inputs, capable of immediately sensing and quickly reacting to vehicle inclination and centrifugal forces, and automatically change spring rate to either hard or soft as needed to provide a quick response leveling effect of the vehicle on uneven terrain and a comfortable ride on level terrain.
Another object is to provide an inclination and centrifugal force-sensitive dual spring rate strut that is more stable when embodied as a long travel strut, with piston strokes greater than 6xe2x80x3, where current long travel strut offerings either only slow suspension deflection by increasing gas or fluid dampening restriction, or increase spring rate with velocity sensitive valves which close or restrict communication to a secondary chamber after a significant suspension deflection.
In the present invention, valve ports close immediately in response to vehicle inclination or centrifugal force to confine strut gases within the primary chamber to provide a hard spring rate on the high load side of the vehicle. When communication ports between the primary and secondary chambers are open, the strut piston, while traveling the same linear distance as before, is now compressing its gases within a much larger combined volumetric area, thus providing a soft spring rate.
Vehicle inclination is detected by a gravity-sensitive rotating weight mechanically coupled to open or close a pilot valve which directs pressure differentials, created by strut piston pumping action within the primary chamber, to pressurize one side of a sliding high gas volume spool valve, which moves within its own cylinder, changing said spool""s port positions to either open or close gas flow communication between the primary and secondary chambers.
Said spool, being approximately {fraction (1/7)} the surface area of the strut piston, requires only a minute portion of the volumetric high pressure displaced by an approximate 0.07xe2x80x3 strut piston compression stroke linear deflection to achieve full stroke port position change, thereby achieving a quick response to pilot valve pressure input signals. Overall, spring rate change is virtually immediate with this valve sequence.